Hazard types, including allergens

Codex defines a hazard as a biological, chemical or physical agent in food with the potential to cause an adverse health effect.

Biological hazards are usually the biggest concern. Norovirus is the most common cause of gastroenteritis in the UK, and Campylobacter is the most common bacterial cause of food poisoning. Bacteria need food, moisture, warmth and time. Some can double every 10 to 20 minutes, which is why time and temperature control matter so much.

Some bacteria need special thought. Listeria monocytogenes can grow at chill temperatures, so ready-to-eat chilled food is the risk. Bacillus cereus, found in cooked rice, and Clostridium perfringens, found in large meat dishes cooled slowly, form spores that can survive cooking. Staphylococcus aureus and Bacillus cereus can produce toxins.

Chemical hazards include cleaning products, pesticides, veterinary drug residues and mycotoxins, which are poisons made by moulds. A common kitchen cause is cleaning chemical poured into an unmarked bottle.

Physical hazards include glass, metal, hard plastic, stones and bone. They can come from ingredients, equipment, packaging, premises and people.

Allergens need special care. The Codex definition has three groups, and its guidance on hazard analysis lists allergens among the chemical agents. Many UK businesses list allergens as a fourth group so that they are not overlooked. Either way is fine, as long as allergens are properly assessed.

The 14 allergens are celery, cereals containing gluten, crustaceans, eggs, fish, lupin, milk, molluscs, mustard, tree nuts, peanuts, sesame, soya, and sulphur dioxide and sulphites. Allergen cross-contact means an allergenic food getting into another food by accident. Cooking does not remove allergens. So control depends on separation, cleaning and accurate information. Typical failures are a supplier changing a recipe, a shared scoop, a shared fryer, or the wrong label.

Be specific. Codex says hazards should be specific and their source should be described. 'Physical hazard' tells nobody what to do. 'Metal fragments from a broken blade at the chopping step' does.

At each step, ask three questions. Could a hazard get in? Could it grow or increase? Could it survive?

A hazard analysis has two stages. First, list all the potential hazards at each step. Second, evaluate them to find the significant hazards. A significant hazard is one that is reasonably likely to occur at an unacceptable level if there is no control, and for which control is essential given the intended use of the food.

To judge this, consider likelihood and severity. Likelihood is how probable the hazard is, taking account of your prerequisites. Severity is how bad the harm would be. Who eats the food matters too. The same hazard is more serious in a care home or a nursery.

Weigh both together. A hair in a sandwich is quite likely, but it is unlikely to cause serious harm. Peanut in a meal sold as peanut-free may be much less likely, but it could kill someone. A low likelihood does not make a severe hazard safe to ignore.

A control measure is any action or activity that can be used to prevent or eliminate a hazard, or reduce it to an acceptable level. An acceptable level is a level at or below which the food is considered safe for its intended use. One hazard may need more than one control measure, and one control measure may control more than one hazard.

Here is a short example from a cafe making hot chicken rolls. In storage, bacteria could grow, so the control is chilling. At cooking, bacteria could survive, so the control is heat. At assembly, bacteria could get in from raw meat, so the control is separate boards and clean hands. Sesame on the rolls could get into a sesame-free order, so the control is separate utensils and a clear order system.